In U.S. Pat. No. 4,232,667 there is disclosed a single limb or unilimb anesthesia breathing circuit in which the inspiratory and expiratory tubes are positioned with one tube inside the other. Such a construction is advantageous in preventing twisting between the two tubes which could lead to accidental disconnection as well as to reduce the clutter of anesthesia equipment in the limited surgery area. Another important advantage is improving temperature and humidity maintenance by housing the inspiratory tube entirely within the lumen of the larger diameter expiratory tube. The by-product of absorbing carbon dioxide by soda lime is heat and humidity. The heat and humidity carrying capacity of the inspiratory tube in a two-tube system is compromised due to the cooling of the uninsulated inspiratory tube. In this circuit the warm exhaled breath insulates the inspiratory tube, thus dramatically increasing the capacity of the inspiratory tube to carry heat and humidity to the patient.
Other examples of unilimb anesthesia breathing systems are disclosed in U.S. Pat. Nos. 3,856,051, 4,007,737 and 4,265,235. However, none of the aforesaid breathing tube circuits are provided with a patient end fitting to which both inner and outer tubes are secured with a gas-tight seal, and which is also fully rotatable at the patient end of the assembly. The aforesaid prior art apparatus do not have practical methods for easily and readily testing the gas-tight seal between the tubing components and the end fittings of the assembly. Such checking is not only desirable, but is often required in anesthesia apparatus check out procedures.